This invention relates generally to mufflers for carrying away the combination of exhaust gases and cooling fluid coming from a marine engine, and more particularly, to a compact, inverted flow marine muffler which provides improved attenuation of the exhaust noise generated by operation of marine engines.
Internal combustion engines utilized in watercraft standardly use the water supporting the craft for engine cooling purposes. The water is drawn into the craft and circulated through an engine cooling jacket or engine coolant heat exchanger. The water is then commonly ejected into the exhaust system to cool the combustion gases such that they might be safely discharged through the hull of the craft without presenting a fire hazard. Accordingly, a marine exhaust muffler must handle not only exhaust gases, but also the waste cooling fluid or water which is discharged from the craft through the exhaust system.
In addition to safely handling exhaust gases and waste coolant water, a marine muffler, as its name implies, should muffle or attenuate the exhaust noise generated by operation of the marine engine. Muffling of exhaust noise from marine engines has been handled in a number of ways. For example, the exhaust may be discharged below the water level. Such muffling is performed in outboard engines and inboard/outboard installations wherein the exhaust is routed through the drive unit such that the exhaust gases and waste cooling water are discharged through or adjacent the propeller driving the craft. In direct drive watercraft wherein no comparable drive unit is provided, it is not practical or convenient to run the exhaust along this route.
For direct drive applications, mufflers of various designs have been placed in the exhaust conduit running between the engine and the discharge. Often, these muffler designs are in-line closely akin to the mufflers utilized on automobiles, but constructed of materials, such as fiberglass, which can better tolerate the marine environment. While such mufflers are currently in high use in the boating industry, they do not provide good attenuation of the noise generated by marine engines. Loud exhaust noise can contribute to fatigue and diminish tne pleasure of boaters, for example, by interfering with audio entertainment and communications on board the craft.
Other more effective muffler designs are available. For example, a cannister or drum exhaust muffler system, is disclosed in U.S. Pat. No. 3,296,997, issued to Hoiby et al. on Jan. 10, 1967. This muffler is particularly applicable to engines which are mounted below the water line in large watercraft. Unfortunately, while this drum muffler design is more acoustically effective than the common in-line muffler, it has considerable bulk and provides an upward pumping action and discharge, which of course is the desired intent of the drum muffler.
There is thus a need for an improved compact muffler design for a marine engine which can safely handle the combination of exhaust gases and cooling fluid from a marine engine and also provide improved attenuation of the exhaust noise generated by operation of the marine engine.